Underground fluid storage tank



Dec. 23, 1969 K. R. oHRER UNDERGROUND FLUID STORGE TANK 2 Sheets-Sheet 1Filed June 11, 1968 INVENTOR. KARL R. ROHRER ATTORNEYS Dec. 23, 1969 K.R. llam-mm 3,485,049

UNDERGROUND FLUID STORAGE TANK Filed June 11, 1968 2 Sheets-Sheet 2 2lb80 l/ /w l AW INVENTOR. KARL R. ROHRER ATTORNEYS United States Patent O3,485,049 UNDERGROUND FLUID STORAGE TANK Karl R. Rohrer, 264 KenilworthDrive, Akron, Ohio 44313 Filed June 11, 1968, Ser. No. 736,109 Int. Cl.B65g 5/00; EZlf 17/16 U.S. Cl. 61-.5 9 Claims ABSTRACT OF THE DISCLOSUREA method of storing fluids in a subterranean cavity including placing aflexible substantially fluid impermeable membrane on the bottom andsides of the cavity and substantially lling the cavity with an aggregatesuch as gravel or other hard filler material and covering this materialwith another flexible impermeable membrane. Inlet and outlet meansinterconnect the interior of the storage unit thus formed with a sourceof lluid supply and the earth is then back-filled over the top or secondmembrane up to the desired grade level.

BACKGROUND OF THE INVENTION This invention basically relates to theunderground storage of fluids such as overflow storm water from a sewersystem, for example, while permitting full utilization of the landoverlying the tank. The inventive concept, which is essentiallydescribed herein in relation to the storage of liquids, can be utilizedfor the underground storage of any desired fluid.

DESCRIPTION OF THE PRIOR ART The following prior art is known toapplicant: Hodges, U.S. Patent No. 870,433; Warren, U.S. Patent No.3,068,- 654; Crawford et al., U.S. Patent No. 3,113,699, and CanadianPatent No. 696,484.

None of the art listed above discloses the inventive concept herein setforth. For example, Crawford discloses an underwater storage systemwhile the Canadian patent discloses an inflatable device and Hodgesshows a simple drainage pit.

SUMMARY OF THE INVENTION In conventional underground storage systems, acavity is first excavated and then a rigid storage tank is constructedwithin the cavity. This is usually a concrete structure which is thencovered with earth and provided with the necessary inlet and outletmeans.

The disadvantages encountered in utilization of such conventionalsystems, in addition to the obvious expense involved in construction,are twofold.

First, there is a problem of utilization of the surface area above thetank due to the lack of sufficient support to enable this area to beutilized for conventional purposes such as buildings, parking lots, etc.

Second, and on the other hand, if the tank is strengthened to asufficient degree to enable the overlying ground surface to be utilizedfor other purposes, the cost factor is considerably increased so as tomake the same nearly prohibitive.

In some other conventional storage systems, open lagoons are used butproblems are encountered with evaporation and also the land area cannotbe used for any other purposes. Rubber tanks are also sometimesemployed, but here again, the overlying surface is not capable of usefor buildings, for example, due to a lack of support.

It has been discovered, therefore, that the above noted disadvantagescan be overcome by providing a cavity into which a flexible impermeablemembrane is laid. The cavity is then substantially filled with gravel orother ice similar aggregates and a second membrane can be placed overthe filler material.

It is known that a certain ratio of void volume remains in a givenvolume of aggregate such as gravel so that storage volume of the tankcan thus be readily calculated.

Inlet and outlet means are provided to interconnect the interior of thetank thus formed to the source of supply for the uid and -overflow andventing means can also be provided.

It has also been discovered that after the second membrane is placedinto position, that. the earth can be back-filled up to the existing orany desired grade level and that due to the structure of the tank, thatthis surface can easily and readily be utilized for any desired purposethereby giving a dual use to a given area of land.

Accordingly, production of an underground storage system having theabo-ve noted characteristics becomes the principal object of thisinvention with other objects thereof becoming more apparent upon readingthe following brief specification considered and interpreted in view o-fthe accompanying drawings.

In the drawings:

FIGURE 1 is a top plan view of the improved underground storage tank.

FIGURE 2 is an elevational view taken on the line 2-2 of FIGURE 1partially broken away.

FIGURE 3 is an enlarged partial view of the point of interconnectionbetween the top and bottom membranes.

FIGURE 4 is an elevational view, partially broken away, of a modifiedform of the invention.

FIGURE 5 is an enlarged perspective view of the inlet and outlet meansof FIGURE 4.

FIGURE 6 is an elevational view, partially broken away, of anothermodified form of the invention.

Considering first then FIGURES 1 and 2, it will be noted that a cavity10 is provided in the earth with the dimensions thereof being determinedby the quantity of fluid that the system is intended to accommodate andwith this quantity being calculable due to the ratio of void volume thatwill remain in a given amount of aggregate. It should be noted thatwhile a particular configuration is shown with regard to the cavity thatthe invention is not intended to be limited to any particular size orshape.

A shallow trench or depressed area is also provided around the topsurface of the cavity for reception of an overflow pipe and the edges ofthe membranes as will be subsequently more fully described.

Considering next then the storage tank 20 per se and referringparticularly to FIGURE 2, it will be noted that the same comprises aliner or lining means which is shown as a first flexible impermeablemembrane 21 which is laid into the bottom of the pit so as to cover thebottom and substantially lall of the side walls thereof. This membranemay be of any suitable material such as clay, plastic or rubber, forexample.

The peripheral edge 21a of membrane 21 is then laid into the trenchwhich has been described above and an overflow pipe 50 can be laid onedge 21a. This pipe 50 is either slotted as at 51 or perforated tocommunicate between the interior of the completed tank 20 and thesurrounding earth and need only extend along a portion of the rim of thecavity. Actually this pipe can feed overflow to any desired point and,in the case of storm water, would probably lead to a stream, forexample. l

The inner surface of the membrane 21 is next filled with a fillermaterial or aggregate 30 which can be of any suitable hard material inparticle form such as gravel or boulders, for example.

After the interior of the cavity, which is covered by the first membrane21, has been filled with the storage media comprising the fillermaterial 30, a second membrane 22 is laid over the gravel so as tocompletely cover the top surface thereof. It should be noted here thatthe peripheral edge 22a of membrane 22 is tucked around edge 21a ofmembrane 21 and 'pipe 50 in the form of the invention shown so that whenthe cavity is back-lled, as will be described below,a secure seal Can beobtained. It is also possible to merely lay edge 22a of membrane 22 overedge 21a of membrane 21 or the edges may be positively secured togetherif desired by stitching, cementing or other conventional means. Y

Inlet and outlet means, generally indicated by the numeral 40, are shownlocated in the bottom of the tank formed by the membranes 21 and 22although their location is a matter of choice. These means generallyinclude a connecting pipe 41 and iilter means 40a adapted to filter outthe larger particles. The pipe 41 of inlet and outlet means 40 isconnected to a source of liquid supply such as, 'for example, a stormsewer (not shown).

It should be noted here that when the tank is used in conjunction with asewer system that conventional means for chlorinating the water can beinstalled in the pipe 41 of inlet and outlet means 40.

Once the installation has been completed by positioning the secondmembrane 22 in place, the earth can be backiilled to the existing gradelevel or to any other level as clearly shown in FIGURE 2.

At this point, the tank 20 is ready for the reception of uids and thesurface of the earth S is ready for utilization for any desired purposefor which such land would be normally utilized with the aggregate orfiller material 30 supplying the necessary support.

In use or operation the fluid can be introduced into the tank throughpipe 41 by a pump or by gravity from the source of supply. The tank canbe utilized as a semipermanent storage means if desired but is mainlyenvisioned as a temporary storage device and removal of the liquid canalso be accomplished through pipe 41 by conventional pumping means whendesired.

It should be noted here that while certain materials have been suggestedas suitable for the membranes 21 `and 22, that the inventive conceptherein disclosed is not intended to be limited to any specific materialand any material which is substantially impermeable and has some degreeof exibility to enable it to conform to the contour of the pit or cavitymay be utilized.

Similarly, while the iiller material has been illustrated as gravel, itis believed apparent that any material having a suitable hardness andresistance to being crushed may be utilized. Similarly, the invention isnot intended to be limited to any particular size with regard to theparticles which make up the ller material.

It should also be noted that overflow pipe 50 is generally necessarywhen liquids are being stored but may be dispensed with if theinstallation is designed for the storage of gases.

Turning next then to FIGURES 4 and 5 which show a modified form of theinvention, it will be noted that a cavity a is provided similar to thecavity provided with` regardto the form Of the invention shown inFIGURES 1, 2 and 3. The bottom membrane 20a and top membrane 2lb arealso identical in this form of the invention.

Similarly the interior of the4 cavity is filled with a filler material.30 as noted above. However in this instance, a layer of fines, such asthe sand 31, is provided on the bottom membrane a before the llermaterial 30 is inserted. This layer of sand prevents punctures orruptures in the membrane 20a either due to the jagged or rough surfacesof the. particles -of the filler material or due to the weight of theoverlying earth pressing such particles against the membrane.

This form of the invention also discloses a specific form of inlet valvesuitable for use with regard to either the tank shown in FIGURES l, 2and 3 or that shown in FIGURES 5 and 6.

This valve is principally illustrated in FIGURES 4 and 5 and isgenerally indicated by the numeral 60. This valve has a series ofvertical float guides 61, `61 which are held in place by a plurality ofannular support rings 62, 62 which may be secured to guides 61, 61 byWelding or other suitable means. The structure formed by the supportrings and float guides is mounted on a scour plate 63 which is in turnmounted on the end of the inlet and outlet pipe 41.

A iloat is shown received within the iioat guides and is adapted to movevertically within the guides 61, 61. It is believed apparent that uponthe entry of liquids through the pipe 41 that the oat 70 will rise andsimilarly that as liquids are pumped out of the tank that the float 70will return to its seated position on the scour plate 63. The action ofthe liquid as it is passed out of the tank will cause float 70 to have ascouring action in conjunction with plate 63 for sediment removalpurposes.

An access cover is also provided for seating on the top support ring 62and is designed so as to be readily removable so that the valvemechanism can be cleaned when necessary. It is believed apparent thatthis cover 80 can be mounted in flush relationship with the earthssurface so as to not interfere with the secondary uses of the land.Cover 80 also can be provided with apertures S1, 81 to serve as a ventto prevent an air lock during lling of the tank. If desired, when gasesare being stored, cover 80 can be imperforate in which case aconventional venting system can be run from the cover to an open ilame,for example.

Float guides 61, 61 also can be provided with a series of perforations61a, 61a which can be attached to suitable spray means so that thevalving system can be ushed when desired.

In this regard, FIGURE 5 shows a tube or rod 90 leading away from hollowring 62 to a suitable Source of pressurized liquid 91 which isillustrated schematically. Thus, liquid can be forced through tube orrod and thus through the perforations 61a, 61a of guides 61, 61 to flushthe valve when desired.

In addition to the form of the invention described above, it is believedthat the inventive concept herein disclosed is also applicable toexisting installations. Thus, in FIGURE 6 an existing reservoir 100 isshown. In order to employ the invention in conjunction therewith, it ismerely necessary to ll the existing reservoir bed or lining 101 withaggregate 130 and cover the same with membrane 122 following which theearth may be back-lled as described above.

In this way, the existing reservoir can still be utilized for storagewhile the land over it can be used for other purposes as well.

It should be noted here that while the inventive concept disclosed ingeneral with regard to the tank per se can be utilized with any fluidincluding liquids or gases, the valving arrangement 60 is primarilydesigned for utilization with liquid storage.

It is believed apparent, therefore, that a new and improved undergroundstorage tank has been disclosed which presents a considerable savings incost over the conventional storage tanks while providing increasedutilization of the land overlying the tank.

It is also believed pertinent to point out that the unique tankdisclosed herein is not subject to deterioration as is the case withconventional tanks and accordingly, utilization of the overlying surfaceof the land is further enhanced by this feature.

It should also be noted that while a hopper shaped cavity is shown, thecavity could take any desired shape due to the -exibility of themembranes 21 and 22 in the form of the invention shown. Furthermore,this characteristic of the membranes makes it possible to avoid the needfor precise grading of the bottom and sides of the cavity since themembranes can accommodate themselves readily to minor irregularities.

What is claimed is:

1. A tank for storing uids in a subterranean cavity of the characterdescribed, comprising;

(A) bottom lining means covering the bottom and at least a portion ofthe sides of said cavity;

(B) a `quantity of filler material disposed on said lining means andsubstantially filling said cavity;

(C) a top impermeable membrane covering said filler material andoverlapping the peripheral edges of Said lining means; and

(D) inlet and outlet means interconnecting the interior of said cavitywith a source of fluid.

2. The device of claim 1 further characterized by the fact that saidbottom lining means includes a bottom flexible, impermeable membrane.

3. The device of claim 1 further characterized by the presence of filtermeans connected to said inlet and outlet means between said source offluid supply and the interior of the tank formed by said lining meansand said top membrane.

4. The device of claim 3 further characterized by the presence of meansfor ushing said lter means.

5. A device of claim 3 wherein said filter means comprises:

(A) a body portion interconnecting said inlet and outlet means and theatmosphere;

(B) a float carried interiorly of said body and adapted to movevertically therewithin in response to the entry and withdrawal of saidfluid into and out of said tank.

6. The device of claim 2 further characterized by the presence of alayer of fines on said bottom membrane beneath said liller material.

7. The device of claim 1 further characterized by the presence ofoverflow means communicating between the interior and exterior of saidtank.

8. The device of claim 1 further characterized by the presence ofventing means adapted to communicate the interior of said tank with theatmosphere.

9. A method of constructing a subterranean Storage tank for liquidsincluding the steps of (A) excavating a cavity;

(B) lining the bottom and at least a portion of the walls of said cavitywith a ilexible, impermeable membrane;

(C) placing a quanity of hard ller material on Said rst membrane;

(D) covering said filler material with a second flexible impermeablemembrane;

(E) interconnecting the area between said rst and second membranes witha source of liquid supply; and

(F) covering said second membrane with earth to grade level.

References Cited UNITED STATES PATENTS 870,433 11/ 1907 Hodges.1,051,344 1/1913 McKnight 61-10 2,755,630 7/1956 Freyssinet 6l.53,052,380 9/1962 Prins 61-.5 X 3,068,654 12/1962 Warren. 3,113,699 12/1963 `Crawford et al..

FOREIGN PATENTS 696,484 Canada.

PETER M. CAUN, Primary Examiner

